GST Calculator

How to use this GST calculator

Pick your GST slab, enter the amount, and choose whether the price is exclusive or inclusive of tax. The tool splits intra-state tax into CGST and SGST halves, or shows IGST for inter-state cases. Everything runs in your browser — no login, no data sent to a server.

GST exclusive vs inclusive

Exclusive (add GST): the amount you enter is the base price before tax. The calculator adds GST on top and shows the gross total. Use this when a vendor quotes ₹10,000 plus 18% GST.

Inclusive (remove GST): the amount already includes tax — like a restaurant bill or MRP-style pricing. The calculator backs out the net amount and shows how much of the total was tax. Use this when you only know the final figure and need the pre-tax base for invoicing or margin math.

The reverse calculation almost everyone gets wrong

This is the single reason the inclusive mode exists. When people have a tax-inclusive total and want the base price, the instinct is to subtract the percentage. That is arithmetically wrong, and it is wrong in a direction that quietly understates your base every time.

Take a ₹1,180 invoice at 18% GST. Subtracting 18% gives ₹1,180 − ₹212.40 = ₹967.60, which is not the answer. The correct base is ₹1,180 ÷ 1.18 = ₹1,000, and the tax portion is ₹180. The subtraction method is off by ₹32.40 on a single small invoice, because the 18% was applied to the base, not to the total — so you have to divide it back out rather than take a percentage off the top.

The error scales with the rate. At 5% the gap is small enough to look like a rounding difference; at 28% it is large enough to distort a margin calculation badly. If you have ever reconciled a tax figure and found yourself a few hundred rupees short with no obvious cause, this is usually where it came from.

CGST, SGST, and IGST — and what actually decides which

For sales within the same state, GST is split equally: half goes to the centre (CGST) and half to the state (SGST). For sales across state lines, the full rate applies as IGST. The total is identical either way — 18% is 18% whether it appears as one line or two — so the split affects how the invoice is written and where the revenue is credited, not what your client pays.

The part that trips people up is that it is not decided by where you are sitting. It is decided by the place of supply, which for most services is the location of the recipient. A developer in Patna billing a company registered in Bengaluru raises an IGST invoice, even though the work happened entirely in Bihar. Billing a client registered in your own state, from the same desk, makes it CGST plus SGST. Getting this backwards means an invoice your client cannot properly claim credit on, and it is the correction that takes the longest to unwind.

A note on rounding

This calculator displays two decimal places, which is right for checking a figure but is not always how the final invoice should read. GST amounts on an invoice are conventionally rounded to the nearest rupee, and rounding each line separately rather than rounding the total can leave you a rupee or two away from what accounting software produces. That difference is harmless for a sanity check and worth reconciling before anything gets filed.

What this calculator does not handle

It covers the ordinary case: a known rate applied forward or backward, split intra-state or inter-state. It does not model reverse charge, where the recipient pays the tax instead of the supplier. It does not handle the composition scheme, which uses entirely different rates and rules for small businesses. It does not deal with exports and zero-rated supplies, input tax credit, TDS or TCS deductions, or the cess that sits on top of the 28% slab for some goods.

Those cases are genuinely not calculator problems. If your situation involves any of them, the number you need depends on facts a form cannot see, and a chartered accountant is the cheaper option in the end.

Common GST slabs in India

• 0% — essential foods, milk, eggs, fresh vegetables
• 5% — packaged food, transport, basic medicines
• 12% — mobile phones, computers, processed food
• 18% — IT services, restaurants, personal care (most common for freelancers)
• 28% — luxury goods, cars, aerated drinks

Who this tool is for

Freelancers quoting clients, shop owners checking invoices, students learning Indian tax basics, and anyone who needs a quick sanity check before filing or sending a bill. It is a calculator, not tax advice — for complex cases (reverse charge, composition scheme, exports), talk to a chartered accountant.

Frequently asked questions

What is the difference between GST exclusive and GST inclusive?

Exclusive means the price does not yet include tax, so GST is added on top to reach the final amount. Inclusive means the tax is already inside the figure you are looking at, so the base price has to be extracted back out of it. A vendor quoting "₹10,000 plus 18% GST" is quoting exclusive; a restaurant bill or an MRP is inclusive.

How do I calculate GST in reverse from an inclusive amount?

Divide rather than subtract. The formula is Net Price = Gross Price × (100 ÷ (100 + GST Rate)), and the tax portion is the gross minus that net. For ₹1,180 at 18%, the base is ₹1,180 ÷ 1.18 = ₹1,000 and the GST is ₹180. Subtracting 18% from ₹1,180 gives ₹967.60, which is wrong by ₹32.40, because the rate was applied to the base and not to the total.

How do I know whether to charge CGST plus SGST or IGST?

It depends on the place of supply, not on where you are working from. For most services the place of supply is the location of the recipient, so billing a client registered in another state means IGST even if you never left your own. Billing a client registered in your state means the rate is split equally into CGST and SGST. The total the client pays is identical either way.

What are the GST slabs in India?

The primary slabs are 0% for essentials such as milk, eggs, and fresh vegetables; 5% for packaged food, transport, and basic medicines; 12% for mobile phones, computers, and processed food; 18% for IT services, restaurants, and personal care, which is the rate most freelancers and agencies deal with; and 28% for luxury goods, cars, and aerated drinks, some of which carry an additional cess.

Why does my invoice software show a slightly different figure?

Almost always rounding. This calculator shows two decimal places, while invoices are conventionally rounded to the nearest rupee, and rounding each line item separately gives a different total than rounding once at the end. A gap of a rupee or two is normal; anything larger usually means the exclusive and inclusive modes have been mixed up somewhere.

Is this a substitute for professional tax advice?

No. It handles a known rate applied forward or backward and nothing else. Reverse charge, the composition scheme, exports and zero-rated supplies, input tax credit, TDS and TCS, and cess on the 28% slab are all outside what it models, and each of those depends on details a calculator cannot see. Use it to check a number, not to decide a filing position.